This invention has to do with vibration test apparatus and more particularly is concerned with a hydrostatic bearing apparatus useful in vibration testing. In particular the apparatus provides a bearing for test piece oscillation which accommodates temperature induced dimensional changes in the test piece.
The use environment of many electronic and mechanical components requires evaluation of the component for vibration stability. Typically the component or piece to be tested is mounted for vibrational movement in a single axis at a predetermined rate, induced by a shaker-head coupled to the test piece per se or to a jig supporting the test piece. The test piece is supported on a slip plate and the slip plate in turn is supported on a bearing table which insures the necessary axially directional movement. Because test criteria require faithful replication of the test protocol, the need to have freedom from extraneous sideways movement, or other than test axis movement, is paramount.
Certain test pieces are so large that they are not conveniently carried upon conventional bearing structures. And for these test pieces special bearing devices must be used. Other test pieces are sufficiently large that the ordinarily experienced changes in temperature in the test environment cause conventional bearing structures to bind, and thereby induce extraneous axes of movement into the test procedure, skewing results, and making the test unreliable.
It is accordingly a major object of the present invention to provide a novel hydrostatic bearing apparatus which is responsive to dimensional changes in the test piece, induced by temperature changes, but which, withal, maintains a uniaxial test direction.
This and other objects of the invention, to become apparent hereinafter, are realized by a novel hydrostatic bearing apparatus in which the bearing locus is bodily displaceable responsive to dimensional changes in the test piece, whereby binding and extraneous non-test axis movement is avoided and true test results obtained.
More particularly, the invention provides a hydrostatic bearing apparatus adapted to mount a shaker-coupled dimensionally temperature dependent test piece for vibratory oscillation along a predetermined axis in which the apparatus comprises a support block having a compliant section defining a bore, a shaft axially journaled in the bore and defining therewith a bearing locus paraxial with the test axis, and bracket means securing the test axis to the shaft beyond the locus for bearing-guided test axis oscillation, the bearing locus being test axis paraxially bodily displaceable responsive to displacement of the compliant section in test piece dimensional change accommodating relation.
Typically, the support block centrally supports the shaft and the bracket means is secured to the shaft ends on either side of the support block. The bracket means typically comprises a saddle having depending ears defining securing means for securing the saddle rigidly to the shaft, and a base portion between the ears adapted to be rigidly fastened to the test piece.
In particular embodiments the test piece may comprise a slip plate driven by a shaker and an assembly to be vibration tested fixed to the slip plate, or the test piece may be comprise an assembly to be vibration tested coupled directly between the shaker and the bracket means. In either instance the apparatus of course may include a shaker coupled to the test piece in vibration transmitting relation.
In more particularly preferred embodiments, for use in a hydrostatic bearing apparatus adapted to mount a shaker-coupled dimensionally temperature dependent test piece for vibratory oscillation along a predetermined test axis, having a shaft, and a bracket coupling the test piece to the shaft; there is provided a shaft support block having a compliant section with a through bore for axially journaling the shaft and defining a bearing locus therewith paraxially with the test axis, the bearing locus being test axis paraxial bodily displaceable responsive to displacement of the compliant section in test piece dimensional change accommodating relation. The support block may include means selectively restraining compliant section displacement, and comprise the compliant section, support walls supporting the compliant section and means defining a section displacement clearance between the walls and the section locally laterally opposite the bore. The mentioned support walls may be separably secured to the compliant section in laterally spaced relation therefrom to define the displacement clearance. The securement of the walls to the section generally is above the section bore, and the apparatus further includes means selectively securable to both the walls and the section below the bore to block section displacement.
Accordingly, in one preferred embodiment there is provided hydrostatic bearing apparatus adapted to mount a shaker-coupled dimensionally temperature dependent test piece for vibratory oscillation along a predetermined test axis comprising a support block having a displaceable compliant section defining a bore and means defining a section displacement clearance locally laterally opposite the section bore, a shaft axially journaled in the section bore and defining therewith a bearing locus paraxial with the test axis, and bracket means securing the test piece to the shaft beyond the locus for bearing-guided test axis oscillation, the bearing locus being subject to shaft-transmitted sideways thrust upon temperature change induced dimensional changes in the test piece, the compliant section bearing locus being test axis paraxially bodily displaceable through displacement of the compliant section into the clearance, responsive to sideways thrusting of the shaft in test piece dimensional change accommodating relation.
In such embodiments there is further provided apparatus in which the support block centrally supports the shaft and the bracket is secured to the shaft on either side of the support block, the bracket means comprising a saddle having depending ears having clamping means for clamping the saddle rigidly to the shaft, and a base portion between the ears adapted to be rigidly fastened to the test piece; the test piece includes means for coupling the test piece to a shaker in vibration transmitting relation, whether the test piece comprises a slip plate drivingly coupled to the shaker and an assembly to be vibration tested fixed to the slip plate or whether the test piece comprises an assembly to be vibration tested in directly coupled relation between the shaker and the bracket means.
As in earlier embodiments the support block may include means selectively restraining compliant section displacement and in such embodiments the support block will comprise a compliant section, support walls supporting the compliant section in depending relation and walls defining a section displacement clearance between the walls and the section locally laterally opposite the bore, the support walls being separably secured to the compliant section in laterally spaced relation therefrom to define the displacement clearance, the support wall securement to the section being above the section bore, and there being further included means selectively securable to both said walls and section below the bore to block section displacement.
In a highly preferred embodiment of the invention there is provided hydrostatic bearing apparatus adapted to mount a shaker-coupled, dimensionally temperature dependent test piece for vibratory oscillation along a predetermined test axis, the apparatus comprising a support block having support walls and depending therefrom a displaceable compliant section defining a bore, the walls and section being locally laterally spaced opposite the bore to define a section displacement clearance, a shaft reciprocally axially journaled in the section bore in centrally supported relation and defining with the bore a bearing locus paraxial with the test axis, and bracket means securing the test piece to the shaft at opposite ends thereof beyond the support block section bore, such bracket means each comprising a saddle having depending ears defining split ring clamps circumferentially clamping the saddle to the shaft, and a base portion between the ears for rigidly fastening the bracket to the test piece, for bearing-guided test axis oscillation, the bearing locus being subject to shaft-transmitted sideways thrust upon temperature change induced dimensional changes in the test piece, the compliant section bearing locus being test axis paraxially bodily displaceable upon and to the extent of displacement of the compliant section into the clearance responsive to sideways thrusting of the shaft in test piece dimensional change accommodating relation.
In each of the foregoing embodiments there may further be included also a shaker coupled to the test piece in vibration transmitting relation.